This invention relates to an automatic level control circuit in which, when the level of an input signal is lower than a reference value, the signal is passed as it is without being controlled, when the level exceeds continuously the reference value for a predetermined interval, the output level is decreased to the reference value, and when the level of the input signal is restored to a value less than the reference value, the level control is quickly stopped.
When transmitting a frequency division multiplexed telephone signal with a FM system by utilizing a satellite, for the purpose of effectively using the bandwidth and electric power, the margin for overload is small. For this reason, an automatic level control circuit mentioned above has been used for the transmitter of each ground station so that the level of a multiplexed telephone signal would not exceed a predetermined value over a long time.
A number of such automatic level control circuits have been proposed but such circuits have large size and large temperature dependent variation.